404 PRACTICAL HISTOLOGY. [XXXVIII. 



alone, or first stain in eosin and then in methylene-blue or 

 haematoxylin. For leucocytes the blood of the horse is specially 

 valuable, as the white cells are so large (Sherringtoa). 



33. Fibrin, Hsemin, Cartilage, Muscle, Nerve, and the other 

 tissues are treated as recommended for frog's tissues, and the same 

 is the case with organs. 



34. Salivary Glands and Pancreas. 



Tease a small part of the parotid, or other salivary gland, or 

 the pancreas, in aqueous humour to see the fresh condition of these 

 glands. In the guinea-pig's glands note the zymogen granules. 



A permanent preparation may be made by exposing small pieces 

 to the vapour of osmic acid and mounting in glycerine. In this 

 way the zymogen granules are preserved (Lesson XXIII. p. 265). 



N.B. In this Lesson the methods stated expressly exclude com- 

 plicated methods of hardening and section-cutting. 



ADDENDA. 



A. Altmann's Researches on " Granula " in Cells. 



For those who wish to study Altmann's views on the constitution 

 of the protoplasm and nuclei of cells, and the methods of displaying 

 what he calls his "granula," we must refer to his monograph, 

 entitled Die Elementarorganismen und Hire Beziehung zu den Zdlvn, 

 Leipsig, 1 890, which contains twenty-one beautiful plates. 



B. Obreggia's Method for Paraffin Sections. 



The method of Obreggia (N enrol ogisches CentralUatt, 1890) has 

 been applied by Gulland (Journal of Pathology, 1893) to parafttn 

 sections. The hardened tissues are embedded in paraffin, and 

 ribbons of sections are cut with a rocking microtome or Minot's 

 form. The sections are at once transferred to glass plates coated 

 with the following solution : 



Syrupy solution of powdered candy-sugar made with boiling 



distilled water . . . . . . . . 30 cc. 



Absolute alcohol . . . . . . . 20 ,, 



Transparent syrupy solution of pure dextrin made with dis- 

 tilled water 10 ,, 



Pour this solution over the plates two or three days before they are 



